September 21, 2009

Invasive species spread hard to predict

U.S. researchers say they've determined it will not be easy to scientifically predict the spread of invasive plants and animals.

University of California-Davis Professor Alan Hastings and University of Colorado-Boulder Assistant Professor Brett Melbourne used a tightly controlled laboratory experiment and a mathematical model to reach their conclusion.

When they released 600 identical beetles and allowed them to spread at will through 30 identical landscapes over 13 generations, they noted a surprising degree of difference in the outcome.

The researchers said some beetles went far, traveling across 31 landscape patches in the 15-month experiment, while others went only a third as far. The rest fell somewhere in the middle.

Hastings said the results suggest it won't be as easy as some had hoped to catalog all the factors that influence the spread of an invasion.

There appears to be this intrinsic variability, even in the simplest ecological settings, that means that difficulty in prediction is a basic feature of ecological systems, said Hastings.

If invasion forecasts are to improve, Melbourne said ecologists will have to keep trying to quantify the randomness in environmental and biological processes.

Ecological forecasts will become more like weather forecasts, with a stated range of probability, but not certainty, like when the meteorologist says there is a 75 percent chance of rain on Thursday, said Melbourne.

The study appears in the journal Science.